Can we make callout in salesforce using flows. not invoking an apex class in flows. I'm asking about the entire callout process in flows. is this possible??

@Abdul Yashar @Usman Ali

You can make a callout from the flow without using the apex code. You can use External Services. 

1. Registering an external web service that you submit as an OpenAPI-compliant specification defining the web service
2. Bring the operations of your external web service into the Salesforce platform (invocable actions) for use with point-and-click tools like Flow Builder 

See more information about external services below

 Get Started with External Services